Department of Invertebrate Zoology News - No Bones
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01 March 2018

Tiny Jewels in the Ocean

In the group of marine animals known as echinoderms (from Greek, meaning “spiny skins”), there are five distinct groups alive today – the familiar starfish, sea urchins (including sand dollars), sea cucumbers, sea lilies, and brittle stars. A beachcomber picking things up along the shore, or a deep-sea fisherman sorting his catch in a net, can usually tell at a glance to which group of echinoderms a specimen belongs, for the five main groups have fairly distinctive shapes.

There are about 2,000 species of brittle stars alive today, and most brittle stars are shaped like this (Figure 1), with a small central disc and five so-called arms. But, in 1879, a British scientist, Dr. W.P. Sladen, discovered a strange little echinoderm, about half an inch across, that he at first thought was a starfish – it was certainly starfish shaped - but on further study, he was amazed to find that it was a brittle star. He named this new genus Astrophiura, which might be translated to mean “starfishy brittle star”. In the intervening 100 years and more, about eight additional species of this strange animal have been found, in various areas of the world’s oceans. Until recently, though, none had been recorded from the Atlantic Ocean.

A few specimens, some in the collections of the Smithsonian’s Natural History Museum, and others that have been collected very recently in the vicinity of Curacao in the southern Caribbean, have proven to be Atlantic Ocean representatives of this weird starfishy brittle star, and I have named this new species Astrophiura caroleae in honor of Dr. Carole Baldwin, a Curator of Fishes in our museum, who founded DROP (Deep Reef Observation Project) several years ago, and whose dedication and enthusiasm has resulted in many new deep coral reef discoveries being made using a manned submersible, Curasub, which can dive to depths of 1000 feet and more.

Figure 2. From Pawson, D.L. 2018. Zootaxa 4378 (2).

Astrophiura caroleae, like its weird relatives, is about half an inch across, with a starfish-like central disc, and tiny fragile so-called free arms, which are usually broken off when individuals are collected. This animal (Figure 2A, 2C, 2D) is usually easily visible because of its bright reddish color, and it adheres to hard surfaces, so it can be found attached to dead shells, pieces of coral, and man-made objects – such as discarded beer bottles (Figure 2B).

Does this little creature play an important role in the general economy of the deep sea? Probably not. It is seldom found, but it always excites interest and pleasure. A tiny and beautiful jewel that challenges us to learn its secrets!